Not sure why you think O2 are better than the others - the contracts are all fairly similar (but O2 have just changed their pricing making them less competitive) but reception has as much to do with which network people use as price.Where I live O2's 3G is appalling so I use T-Mobile.

I wasnt sure T-Mobile sold the iPhone as i thought the main companies that were now selling them were Orange and Vodafone.

i did hear they were selling on the quiet re-comissioned (2nd hand) phones but i wasnt sure what the contract was like?
I am coming up to the point where i can change and get a 3gs or maybe wait and see about these 4g rumours but theres nothing really official on that is there?

Mine's an O2 phone, I just use it on T-Mobile.
The ones T-Mob are giving to their valued customers are grey imports not second hand.
The next iPhone will probably be released in July but anything you hear about it is just rumours.

Oh i get you with the T-mobile giving grey imports,
i might as well wait till July and see what happens as i m happy with me Iphone 3g at this point in time.

Provided you activated your phone in iTunes then you will be OK.
You could JB and UltraSn0w having first activated in iTunes and still be OK.
You could JB and hactivate and stay on O2, in which case you would not be OK.
I'm guessing you activated your phone in iTunes first then JB in which case you will be fine.

He who asks a question looks foolish for 5 minutes. He who doesn't ask a question remains foolish forever.

i requested an unlock online from o2 the other week, got a text from them saying it would be unlocked, connected to itunes and its been unlocked.
my contract expires in august this year! still under contract for a while as well!